As mobile communications systems develop, services with increasingly high quality can be provided by the systems. To maintain long-term competitive advantages of the 3rd Generation Partner Project (the 3rd Generation Partner Project, 3GPP) and further improve system spectral efficiency and a user throughput, an LTE-Advanced (LTE-Advanced, LTE-A) standard is formulated, and a carrier aggregation (CA, Carrier Aggregation) technology is introduced to LTE-A. Carrier aggregation means that one user equipment (User Equipment, UE) can use multiple serving cells at the same time to perform uplink and downlink communication.
However, currently, a signaling structure supports aggregation of a maximum of eight cells (including one primary serving cell and seven secondary serving cells, where each cell corresponds to a unique cell index, a cell index of the primary serving cell is invariably 0, and values of cell indexes of the secondary serving cells range from 1 to 7).
However, as system spectral efficiency and a user throughput are further improved, more cells (for example, 32 cells) need to be aggregated. Therefore, how to increase a quantity of to-be-aggregated cells or flexibly change a quantity of to-be-aggregated cells while making no change to a signaling structure and making a relatively slight change to a protocol is a problem that urgently needs to be resolved.